Protective apparatus for parallel transmission-lines.



No. 840,479. PATENTED JAN. 8, 1907. H. P. DAVIS & P. OONRAD. PROTECTIVE APPARATUS FOR PARALLEL TRANSMISSION LINES.

APPLICATION TILED JAN. 30. 1905.

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NVENTOPS by A 60- 2AM BY 7 QQAA QQW TTORN EY PATENTED JAN. 8, 1907. H. P. DAVIS & P. CONRAD. PPARATUS FOR PARALLEL TRANSMISSION LINES.

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APPLIGATION FILED JAN. 30. 1905.

PROTEOTLVE A WITNE ES: @Q

UNITED STATES PATENT OFFICE,

HARRY P. DAVIS, OF PITTSBURG, AND FRANK CONRAD, OF EDGEVVOOD PARK. PENNSYLVANIA, ASSIGNORS TO WESTINGHOUSEQELEGTRIC & MANUFACTURING COMPANY, A CORPORATIONOF PENNSYLVANIA.

PROTECTIVE APPARATUS FOR PARALLEL TRANSMISEON-LINESn Specification of Letters Patent.

Patented Jan. 8, 1907.

' Original application filed January 20, 1904, Serial No- 189.903. Divided and this application filed January 30, 1905. Serial To all whom it may concern:

Be it known that we, HARRY P. DAVIS, a resident of Pittsburg, and FRANK CONRAD, a resident of Edgewood Park, in the county of Allegheny and State of Pennsylvania, citi- Zens of the United States, have invented a new and useful Improvement in Protective Apparatus for Parallel Transmission-Lines, of which the following is a specification, this to application being a division of our application, Serial No. 189,903, filed January 20, 1904.

Our invention relates to apparatus for the protection of high-tension transmission-lines I 5 and its object is to provide means for interrupting the circuit in a line when the direction of flow of energy becomes reversed in any one of the conductors belonging to that line.

v In transmitting electrical energy at high potentials over long distances it is a usual practice to employ two or more parallel lines.

This is done for thepurpose of avoiding the interruption of service which would occur in the event of an accident to a system embodying only a single line. It therefore becomes advisable to employ protective devices the operation of which will affect the injured line only;

Our invention is applicable to systems comprisin one ormore generating-stations from whic energy is transmitted to distributing-points by means of parallel lines, at either or both ends of which we propose to 3 5 place devices which are operated only when the direction of flow of energy through them is opposite to its normal direction, the direction of the flow of energy in alternating-current lines being defined as the direction of the 4 drop of potential.- One or both ends of the line may be protected also by means of ordinary overload devices if desired.

Our invention is illustrated in the accompanying drawin s, in which Figure 1 is a iagrammatic view of a com plete three-phase system with the connections of the devices properly made at distant ends of the lines. Fig. 2 is a view, in side elevation, of a transformer employed in connection with our system, and Fig. 3 is a plan view of the transformer shown in Fig. 2.

Referring now more particularly to Fig. l, a three-phase generator 1 is represented as supplying energy to loads 2 and 3, through conductors 4, 5, and 6, and 7, 8 and 9, the line comprising conductors 4, 5, and 6 being in parallel with thatcomprising conductors 7, 8, and 9. A load 3, comprising suitable translating devices, is supplied from a branch circuit, which is connected to the main line at any desired or convenient point. At the generator end overload circuit-breakers are indicated at 10 and 11, and reverse currentbreakers are indicated in the ends of the branch and main lines at 12. Series transformers 13 and 14, the primaries of which are respectively connected in the conductors 4 and 7 of the parallel lines, have their secondaries connected, respectively, in series with coils 15 and 16 of another transformer 17, a third coil 18 of which is energized only when the flow of energy in one of the coils 15 or 16 is reversed in direction. The coil 18 is connected to the current-winding 19 of a speciallyconstructed instrument 20, which comprises substantially two ordinary wattmeters 21 and 21", havin their movable parts 22 and 22 mechanically connected. The volta ewinding 23 of the wattmeter 21 is supplied with energy through an intermediate transformer 24, from secondarywinding 25 of a transformer 26, the primary Windin 27 of which is connected etween the con uctors 8 and 9. The transformer 24 is so constructed that an operating voltage may be maintained across the terminals of thevoltage-winding 23 of the wattmeter 21 regardless of the fluctuations of the-voltage of the line. It comprises an iron core 28, having. three legs 29, 30, and 31,- in one of the outer ones 29 of which is an air-ga 32, the other enter one 31 being of reduce cross-section. The rimary winding 33 is placed upon the mi dle leg 30 and the secondary winding 34 upon the outer leg 31, having the reduced crosssection. Theiron core at ordinary voltages is oversaturated, the extra flux being forced across the air-gap 32. If the voltage of the line drops considerably, there is still sufficient flux in the.outer-leg'31 of reduced cross- :the direction of the current in one of the con-' ductors 4 and 7. The core 35 f this transformer comprise s three legs 36, 37, and 38, the middle one, 37 ,of which is provided with an air-gap 39, the coil 18 being placed upon the ,middlezleg 37 and the-coils 15 and 16,'respectively, upon .theltwo outer legs 36 and 38.

The coils 15 and 16 are so placed that they produce a circulating magnetic fiux through the outer legsof the iron core. If the direction of the current becomes reversed in either one of these coils, the magnetic flux willbe'forced through the middle leg of the core, thus energizing the coil 18. It is, evidentthat-there can be substantially no flux through the middle leg unless there is a positive reversal of the direction of the current in either the coil 15 or the coil 16, and it is also evident that the relative direction of the current in the coil 18 is dependent upon the line in which the direction of the flow of energy has been-reversed.

'The specially-constructed instrument 20, Which compriseswattmeters 2'1 and 21', is provided for the purpose of selecting the line uponwhich a short circuit or other accident may have occured and for oausin other suitable apparatus to operate to cut '0 lat line out of service. A reversal of the current direction in anyone of the series transformers 13 or 13 or 14 or 14 causes wattmeter-needle 40 to swing against the one or the other of contact-terminals 41 and 42 and close a circuit through a battery 43 and the one or the other of circuit-breaker tripping-coils 44 and 45, according to theline on which the shortcircuit has occurred.

The, direction of movement of the .wattmeter-needle 4O depends upon the relative directions of the currents in the current-coils 19 and 19, which directions are reversed from their normal directions by a reversal of the flowo'f energy in conductors 4, 5, and 6 or in conductors 7, 8, and 9, comprisin the respective lines, because the coils 19 an 19 are respectively in circuit with the transformer-windings 18 and 18 whichare inactive so lon as the line-currents preserve their normal ections, and therefore do not art.

iffers the member 22 or the member 22*- produces a rotative movement of said members in the one direction orthe other, according to thespecific coils energized, and thus moves-the needle 40 into engagement with either the terminal41 or the terminal 42- to close the I circuit of the roper circuit breakertrip-coil. It is to be un erstood that any other suitable device may be employed which will satisfactorilyselect theinjured line. and cause it to'be thrown out-of service'without altering the essential features of our invention.

The operation of the apparatus maybe understood by assuming, for example, a short circuit at 46 between the conductors 4 and 5. The circuit-breakers at 10 being ordinary overload devices will open because of the ex cessive current through them and theshort Energy will then be transmitted.

circuit. from the generator 1 over the conductors -7, 8, and 9 around tothe short circuit at 46, through the series transformer 13 in a'direction which isthe reverse of itsnormal direction. As a result of this reversal the coil 18 becomes energized andtransmits its energy to the current-coil 19 and causes the needle 40-to make contact with the point 41. The battery-circuit is now closed through the circuit-breaker-tripping coil 4.4, and the conductors 4, 5, and 6 are thrown out of service. The apparatus operates similarlyfor a short circuit between any of the other conductors of either line. i

As illustrated in'Figs. 2 and 3, the laminae of the core 35 ofv the transformer 17 are clamped together by means of end plates 47 and bolts 48. The winding 18 may be-divided into two coils 49 and 50, that may be placed on the middle leg 37 of the core.35, substantially as shown. The transformer may assume other proportions and dimensions than those herein specifically shown and described within the scope of ourinvention.

It is evident that we have provided such means for protecting parallel transmissionlines that an injured line, or one on which a short circuit may have occurred, may be auto- 'matically isolated or cut out of service without disturbing the parallel line. By varying a few of the minor details of the connections of the devices our invention may be employed in connection with transmission-lines having'any number of phases, and we do not wlshour lnventlon llmlted, except by such restr ctions as may be imposed by he prior It is to be understood that our invention is not limited to the employment of a single generating-stationfor parallel lines, since the number and location of generating-stations may be varied in accordance with the lengths of the transmission-lines and other conditions of service.

We claim as our invent1on 1. The combination, in an alternating-current system oi electrical distribution having parallel distributing lines, with circuitbreakers therefor, a polyphase-motor device for selecting and energizin the tripping-coil of the proper circuit-lorea er, of means for energizing a winding of said motor device comprisin a transformer having two primary win lugs and one secondary winding, the fluxes induced by the primary windings being normally in the same direction and the secondary winding being energized only when the directions of the fluxes induced by the two primary windings oppose each other.

2. A system of electrical distribution comprising a generating-station, parallel distributing-lines, circuit-breakers in each line near the distributing ends thereof, tripping-coils for said breakers energized from an auxiliary circuit, series transformers the primary windings of which are respectively in series with conductors of the distributing-lines and the secondary windings of which having the same phase are connected to relay-windings Which normally produce fluxes in the same direction in a magnetic circuit, a third relaywlnding which is energized. only when the directions of the fluxes induced by the other two relay-windings oppose each other and means for selecting and closing the proper battery-circuit through one of said trippingcoils.

3. The combination, in an alternating-current system of electrical distribution having parallel distributing-lines and circuit-breakers therefor, of means for selecting and energizing the tripping-coil of the proper circuitbreaker comprising a relay-transformer having two primary windingswhich are respectively energized by currents proportional to the currents in the distributing-conductors and which normally induce fluxes in the same direction in a magnetic circuit, and secondary windings which are energized only whenthe directions of the fluxes induced by the primary windings oppose each other, ourrent-windings in series with said secondary windings, voltagewindings receiving a voltage approximately proportional to the voltage between two of the distributing-conductors, and a switch actuated by said current and voltage windings for closing an auxiliary circuit through either of the said circuitbreaker tripping-coils.

4. In an alternating-current system of electrical distribution having parallel distributing-lines, a circuit-breaker in each of said lines, a polyphase electromagnetic device for closing the circuits of the trippingcoils bf said breakers and means for energizcoils of said breakers, a transformer having primary windings supplied from the respective lines and having a secondary winding connected to one of the windings of the electromagnetic device, the eiiective circuit for the primary magnetic flux being outside the secondary winding except when the current is reversed in one of the primary windings.

6. In an alternating-current system of electrical distribution having parallel distributing-lines, a circuit-breaker in each line, a double electromagnetic circuit-closing device having voltage-coils and current-coils, means for supplying constant voltages from the lines to the voltage-coils and means for supplying current from the lines to the current-coils only when one of the line-currents is reversed from its normal direction.

7 In an alternating-current system of electrical distribution having parallel distributing-lines, a circuit-breaker for each line, a polyphase motor device, one of the windings of which is normally deenergized, and means for energizing said winding when the corresponding line-current is reversed from its normal direction, to effect operation of the corresponding circuit-breaker.

8. In an alternating-current system of electrical distribution having parallel distributing-lines, a circuit-breaker for each line, a polyphase-motor device for closing the circuits of the circuit-breaker tripping-coils, one of the field-windings of which is normally deenergized, and a transformer for energizing said winding when the current in the corresponding line is reversed.

In testimony whereof we have hereunto subscribed our names this 25th day of January, 1905.

HARRY P. DAVIS.

FRANK CONRAD. Witnesses CAROLINE E. SMYERS, BIRNEY HINEs.

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